Statunitian is an alternative nationality form of American, since this gentilic generates ambiguity with 'inhabitants of the
United States of America' and 'people who are born in the Americas (continent)'. It's important to state that Statunitian is not to substitute or eliminate the denonym American, but to solve the ambiguity of the
word. In the international community, most people
don't refer to the USA as America, but rather 'the United States' or similar words.
Similar gentilics are available in other languages (some romance languages) like Spanish (estadounidense), spoken by 460 million people, Portuguese (estadunidense), spoken by 220 million people and Italian (statunidense), spoken by 65 million people.
Person A: "Hey, I'm from Italy, where are you from?"
Person B: "I'm from
America."
Person A: "Where in
America?"
Person B: "I'm from Temple,
Texas."
Person A: "Oh, so you're a Statunitian."
Person B: "A what?"